As customer demand requires improved integrated circuit (IC) performance, new demands are placed on the IC packaging industry. To accommodate such demands, the IC packaging industry has had to produce faster, more reliable, and higher-density circuits while minimizing size. IC packaging must not only meet these performance demands but must also protect against various environmental conditions like moisture, contamination, mechanical vibration and temperature variations. Therefore, the correct packaging of an IC permits the microchip to function in various customer environments, such as, notebook computers, cellphones, video cameras, automobile engine compartments, portable music players, and even between the plastic layers of credit cards.
Integrated circuits can be packaged by a variety of packaging systems. One of the more common types of packaging systems is plastic packaging. Generally, plastic packaging includes the following steps: mounting IC elements to an IC pad portion of a leadframe; electrically connecting bonding pads of the IC elements to the lead portions of the leadframe with bonding wires; sealing the IC elements, bonding wires and leadframe with a molding resin; and dicing the leadframe into discrete packages.
Some of the more common types of plastic packaging techniques employed are dual in-line package (DIP), single in-line package (SIP), and thin small outline package (TSOP). The electronic devices utilizing such packaging are constantly shrinking in size while demanding increased processing power. As these faster and more powerful devices are developed, the number of leads, as well as the number of input/output (I/O) terminals, must be increased to provide power to these electronic devices.
Consequently, the semiconductor industry accommodated such demands by creating quad flatpack (QFP) packaging that employs surface mount technology (SMT). QFP's attain a higher-level lead density by forming leads on all four sides of the package. The QFP has been manufactured with the finest lead pitch for SMT plastic packaging, down to 300 micrometers. A lead pitch this fine is often the limiting factor for high yield QFP packaging because lead shortages can occur at smaller dimensions.
As demand for smaller packaging has persisted, the IC packaging industry further created the quad flat non-leaded (QFN) package. The QFN structure further reduces a packages footprint by terminating the leads at the periphery of the package (i.e.—the flange). Although the QFN structure can reduce an IC packages footprint by eliminating external peripheral lead extensions, the reduced size demands have created an increasingly finer pitch requirement between leads.
QFN packaging is typically either a dual row or single row configuration. Dual row and single row QFN packaging include a molded package, with a flange comprised by a resin and electrical conductors. The electrical conductors are commonly called leads. Of particular noteworthiness, is that the electrical conductors are situated very close together and an electrical conductor to electrical conductor gap (i.e.—the pitch between adjacent electrical conductors) is very small. Unfortunately, this finer pitch requirement has created a serious design flaw, lead-to-lead shorting. As the dimensions between adjacent electrical conductors becomes smaller, electrical cross-talk and lead-to-lead shorting become a design limitation of dual row and single row QFN packaging.
Thus, despite recent developments in QFN packaging, a need still remains for improved QFN package structures and QFN packaging methods for increasing lead density without causing lead-to-lead shortage. In view of the ever-increasing need to reduce packaging size and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.